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A: Atomphysik
A 5: Posters Tuesday (Photoionisation, Multi Photon Processes)
A 5.21: Poster
Tuesday, April 3, 2001, 12:30–15:00, AT3
Above-threshold double ionization of helium — •Manfred Lein1,2, Volker Engel1, and E.K.U. Gross2 — 1Institut für Physikalische Chemie, Universität Würzburg — 2Institut für Theoretische Physik, Universität Würzburg
We use a reduced-dimensional model of the helium atom to study double ionization under the influence of intense laser pulses. We calculate the correlated two-electron momentum distribution and the momentum spectrum of the He2+ recoil ion. We find excellent agreement with experiment. We use the Wigner transformation to analyze the phase-space motion of the electronic center of mass. For long wavelengths (780 nm), the phase-space analysis confirms that rescattering leads to non-sequential double ionization. At short wavelengths, we discover the two-electron analogue to ordinary above-threshold ionization. The total-energy spectrum of the ejected electrons consists of peaks separated by the photon energy. We propose an approximate method to reconstruct the total-energy spectrum from the recoil-ion momentum distribution.